Sexual Development in Phytophthora

本研究将以植物病原疫霉属为模式，阐明卵菌真菌交配和有性孢子发育的发育生物学和遗传学。卵菌是低等真核生物中一个重要但尚未充分研究的类群，包括许多具有经济和环境意义的动植物病原体、其他病原体的生物控制剂和腐殖菌。在卵菌中，就像在许多其他微生物中一样，交配是生命周期中的一个重要元素。交配导致卵孢子的形成，卵孢子是一种耐用的结构，可以随着季节的变化而生存，从而引发疾病流行。性周期也使基因在种群中流动，产生可能更适合的菌株，这是由于决定致病性、宿主偏好、杀真菌剂抗性和其他性状的基因座的新组合。这项提案的大部分内容集中在致病疫霉上，这是一种毁灭性的植物病原体（马铃薯晚疫病），每年造成数十亿美元的损失。也是研究卵菌生物学的良好模式系统。致病疫霉是异宗配合的，当不同交配类型的分离物通过激素相互作用时，通常会诱导卵孢子。在以前的工作中，9个基因诱导交配过程中被确定。在这个项目中，一个多学科的方法将被用来解决这些交配调控基因的功能和调节。这将需要识别额外的调控基因，并为研究其结构，其蛋白质产物的细胞定位，以及沉默和强制表达的影响的基因的子集。除了对致病疫霉的研究之外，还将在同宗配合物种菜豆疫霉中表征基因的表达，菜豆疫霉在单一培养物中产生卵孢子。还将对交配过程中分泌的新化学物质进行初步研究。这项调查的结果将产生概念上和实际上的影响。更好地了解用于指导真核细胞分化，应对压力，并形成生存结构的不同策略。发展中的重要问题将得到解决，如细胞通讯，自我/非自我识别，细胞类型的决定，基因调控和信号转导。同宗配合和异宗配合交配系统的基础也将被阐明。很可能卵菌中的交配调节不同于其他低等真核生物，如子囊菌和担子菌，它们缺乏与卵菌的分类亲和力。从长远来看，如果能够确定控制交配的因素，那么就有可能通过使用合理的基于机制的抑制剂而不是对环境有害的化学品来操纵病原体的生命周期来控制植物病害。

This research will elucidate the developmental biology and genetics of mating and sexual spore development in oomycete fungi, using the plant pathogenic genus Phytophthora as a model. Oomycetes are an important but understudied group of lower eukaryotes that include many economically and environmentally significant pathogens of plants and animals, biocontrol agents of other pathogens, and saprophytes. In oomycetes as in many other microbes, mating is an important element of the life cycle. Mating results in the formation of oospores, which are durable structures that can survive season-to-season to initiate disease epidemics. The sexual cycle also enables gene flow through populations, yielding strains that may be more fit due to new combinations of loci determining pathogenicity, host preference, fungicide resistance, and other traits. Much of this proposal focuses on P. infestans, which is a devastating plant pathogen (potato late blight) that causes many billions of dollars of damage per year. It is also a good model system for studying oomycete biology. P. infestans is heterothallic, and oospores are normally induced when isolates of different mating types interact through hormones. In previous work, nine genes induced during mating were identified. In this project a multidisciplinary approach will be used to address the function and regulation of such mating-regulated genes. This will entail identifying additional regulated genes, and for a subset of the genes studying their structure, cellular localization of their protein products, and the effects of silencing and forced expression. In addition to studies of P. infestans, the expression of the genes will also be characterized in a homothallic species, P. phaseoli, which produces oospores in single culture. Preliminary studies of novel chemicals secreted during mating will also be performed. Results from this investigation will have conceptual as well as practical impacts. A better understanding will be obtained of the diverse strategies used to direct eukaryotic cell differentiation, to respond to stress, and to form survival structures. Important issues in development will be addressed such as cellular communication, self/nonself recognition, cell type determination, gene regulation, and signal transduction. The basis of homothallic and heterothallic mating systems will also be illuminated. It is likely that mating in oomycetes is regulated differently than in other lower eukaryotes such as ascomycetes and basidiomycetes, which lack taxonomic affinity to oomycetes. In the long term, if the factors which control mating can be identified, it might be possible to control plant diseases by manipulating the life cycles of pathogens using rational mechanism-based inhibitors instead of environmentally harmful chemicals.